Electric heater



1937- I w. H. TANGEMAN 2,091,839

ELECTRIC HEATER Filed Oct. 24, 1935 Inventor: William H. Tangeman,

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Patented Aug. 31, 193"! PATENT OFFICE MC HEATER Wllllamll. Tangeman, Ontario, Calif, a-ignor GenerflflectricAIplllnce Edison Ghicago.lll.,acrporationoiNewYork Application October :4, ms, Serial No. 4am 1 Claims. .(Cl. 201-) This invention relates to electric heaters, more particularly to electric heaters of the sheathed type, and it has for its object an. improved method of making a heater of this type.

More particularly this invention relates to electric heaters of the sheathed type wherein a resistance conductor is enclosed by a metallic sheath and is embedded injand supported in spaced relation with the sheath by a densely 0 packed layer of heat conducting, electrically insulating material, such as magnesium oxide. A heater of this type is described and claimed in the U. S. patent to C. C. Abbott No. 1,367,341, dated February 1, 1921.

In many applications it is desirable to bring out both terminals of the resistance element" at one end of the sheath, and it is an object of this invention .to provide an improved method of making a heater of this character.

For a more complete understanding of this invention, reference should be had to the accompanying drawing in which Fig. 1 is a vertical central sectional view of an electric heater arranged in accordance with this invention and showing the heater in one stage of its construction; Figs. 2, 3 and 4 are sectional views taken through thelines 2-2, 3-3 and 4-4 respectively of Fig. 1 and looking in the direction of the arrows; Fig. 5 is an elevation partly in section illustrating the electric heater of Fig. 1, but at a more advanced stage of its construction; and Fig. 8 is an elevation partly in section illustrating the finished electric heater. I

Refen-ing more particularly to Fig. 6, the finished electric heater comprises a metallic sheath ll encasing a sinuous helical resistance conduc-' tor ll. The conductor ll, as shown, is'formed into an elongated loop which extends lengthwise of the heater substantially throughout its length. As shown, the two legs Ill: and lib of this loop are arrangedin substantialb parallel relation with each other and are connected together by a nexus l2 adjacent one end 45 of the heater, the right-hand end as viewed in Fig. 6. TheJengths lid and. llb extend from "this nexus to substantially the opposite end of the heater where the two ends are electricallyand mechanically connected tosuitalfle terminal 50 members ll. While the legs Ila and lib of the resistance conductor may be connected with the terminals It in any suitable manner, I prefer to connect them in the manner described and claimed in United States Patent No. 1.494.938 to 56 C. C. Abbott,-dated my 20, 1924. As there described, the terminalmembers II have their inner ends threaded and are electrically and mechanically connected with the resistance conductor II by screwing a number of the end turns of the lengths lid and lib onto the threaded ends of the terminals. 1 5 As shown, the outer ends of the terminals l3 project somewhat from the sheath ii; The inner ends of the terminal l3 as well' as the legs Ho and llb and'the nexus I! of the resistance conductor .ll are embedded in and supported in 10 spaced relation with reference to the sheath ill .by means of a densely compacted layer oi heat conducting and heat refractory, electrically insulating material it, such as powdered magnesium are spaced somewhat from thecorresponding ends of the sheath, as shown in Fig. 5. Preferably, the ends of the sheath II will be countersunk, as indicated by the numeral ll. The conductor l l is formed by winding it in any suitable winding machine. It is then threaded through a suitable washer ll, which is provided with a pair of apertures I! for the conductor spaced on opposite sides of the center of the washer, as shown in Figs. 1 and 4. The washer isprovided with slits or sheared sections Isa extending from the apertures I! to the edges of the washer to facilitate the assemblyof the conductor with the washer. The conducor 40 is so threadedthat the two legs lla. and lib of substantially equal length protrude through the washer. The part of the conductor lying in the washer B pulled straight to form the straight nexus It. The washer ll is formedct any suitable material which, while being strong enough to support the resistance conductor, is relatively weak mechanically so as to be deformed muermnywhentheheeuhiumuss agemerco will be pointed out in greater detail hereinafter.

A washer formed of mica has been found-to be quite I when the conductor H has been ed with thewasher u, this sub-assemblyis ready to be assembled with the sheath l and the tube l6.

The tube 16 is prepared for the reception of the washer l8 by providing. a plurality of 5 notches 20 in one end, the right-hand end, as shown in Fig. 1, spaced substantially 120 apart. The washer l8 has in general a diameter substantially equal to the outside diameter of the tube l6, but is provided with spaced ears 2| correspondingto the notches 20 in the tube. The washer is assembled with the sheath I0 and tube l6 by inserting it within the sheath with the ears 2| fitted within the notches 20 in the tube l6. When the parts are assembled in this manner, the tube l6 constitutes an abutment against which the washer l8 rests whereby movement of the washer inwardly of the tube is prevented. Rotation of the washer is prevented by the interengagement of the ears 2! with the tube l6.

To assist in the assembly of the conductor H and washer l8with the tubes l0 and I6, two

straight rods (not shown) having threadedends similar to the threaded ends of the terminals may be threaded onto the resistance lengths Ila and llb. These rods are then directed through the assembled tubes l0 and I6 so as to bring the washer [8 into its correct position in the tube assembly and so as to draw the ends of the resistance conductorout of the other end of the tube assembly-the left-hand end, as viewed 1 in Fig. 1. The was her I8 holds thenexus l2 at the right-hand end of the tube assembly, there- I by preventing movementof the nexusinwardly of the assembly and also rotational movement of the nexus relative to the tubeassembly.

The terminals l3 before being assembled with the resistance conductor legs Ila and llb are assembled with a pair of washers 22 and 23 which in general are similar to the washer I8 at the other end of the heater, with the exception that the washer 22 is formed of 'a suitable metal, such as steel, rather than of mica as is the washer la; the washer 23 is also formed of -mica. These washers 22 and 23, however, are

- provided with pair of relatively large spaced apertures- 26 and 25 respectively on opposite sides of their centers arranged to receive and space the terminals l3, as shown in Figs. 1, 2 and 3. These washers, as pointed out above, will be assembled with the terminals before the terminals are applied to the resistance legs. Ila and Mb.

The terminals after assembly with their washers will be secured to the legs Ila: and Nb. This is accomplished by grasping the end of one resistance leg, unscrewing the rod attached to it.-

and threading it on the terminal. The other terminal is applied in av similar manner. After this, the terminal assembly is slid into the left-' hand end of the tube assembly.

The left-hand end of the tube. I6 is provided -with three relatively deep notches 26 spaced 120 apart, while the washer 23 is provided with three ears 2'! similarly spaced and arranged to be received in the notches 26, .whereby the washer 23 is secured against inward and rotational movement relative to the tubes. The lefthand end of the tube is also provided with a second set of notches 28 much shallower than the notches 26 and spaced 120 apart and also spaced from notches 26. These notches '26 receive ears 29 provided on the washer 22. The depth of the notches 26 is substantially equal to the distance between the washers 22 and 23.

. In view of the foregoing construction, it will be observed that the resistance conductor II tosheathis peened or crimped over so as to lock the washer .in place. The recess H has a depth sufiicient to permit the washer 30 to bear against the adjacent end of the tube l6.

The heater assembly shown in Figs. 1, 2, 3 and 4 is now in condition to be loaded with the ma nesium oxide N, which preferably will be in finely powdered form. In order-to provide for the loading of the sheath, each of the washers I8, 22 and 23 is provided with a plurality of spaced apertures 3| through which thepowder may flow from the left-hand end of the sheath to the washer 30 atthe right-hand end so that the sheath may be completely filled fromend to end.

It will be .understood that in loading the sheath, the heater assembly of Fig. 1 preferably will be supported in an upright position with its left-hand end uppermost, and that the powthe sheath is peened or crimped over to rigidly secure the washer 32 in place.

The heater is then ready for the operation which compacts the magnesium oxide. For this purpose, the sheath is passed through a swaging'machine which materially reduces its diameter and elongates its length. M

After the heater has been swaged so as to compact the magnesium oxide, the left-hand end of the heater is trimmed away so as to remove the washer 32, the headed ends of the terminals i3 and the washer '22. The finished heater is shown in Fig. 6.

Preferably, and as shown, the tube l6 will be provided with a. plurality of longitudinally arranged slots 33 spaced circumferentially of the tube. Two of these slots are positioned'directly opposite the resistance legs Ila and llb.- The purpose of these slots is to provide greater clearance, between the resistance conductor and the outer sheath Hi. -It will be observed that-these slots are completely filled with the insulating material in the finished heater.

The washers I6, 22 and 23, it will be observed, function to support the resistance conductor II and its terminals l3 in their correct positions relative to each other and to the sheath III in the loading and swaging operations. Generally, the magnesium oxide will be sufficiently compacted my invention, it will be understood, or course,

that I donot wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States:

1. The method of making a sheathed electric heater which comprises inserting within a metallic sheath a tube having a length shorter than that of said sheath so that the ends of said tube are spaced from the ends or said sheath i'orming a resistance conductor into a loop with its ends adjacent each other, securing terminals to said ends, assembling readily deformable relatively thin washer-like members formed of mica with said resistance conductor and terminals arranged to support them in a metallic sheath, mounting the assembly of said conductor and supporting members within said metallic sheath and tube so that the supports rest against the ends or said tube, interlocking said supports with said tube to prevent relative rotary motion between these members, the supporting members arranged to provide paths through them from one end to the other or said sheath, filling said sheath with an electrically insulating heat conducting material, the paths through said supporting members providing for the flow of said material irom one end of said sheath to the other, and then reducing and elongating said sheath to compact said insulating material, said deformable washer-like said compacting operation so that in said finished heater, said resistance conductor and terminals are supported solely by said insulating material.

I 2. The method of making an electric. heater which comprises inserting within a metallic sheath a tube having a length shorter than that of said sheath so that the ends of said tube are spaced from the ends of said sheath, windings resistance conductor into a helical coil, threading the end portions of said coil through a readily destructible support, bringing said end portions adjacent each other to form a loop, the nexus of which is mounted-in said support, providing apertures in said support, mounting terminals in a similar support,""securing said terminals to said end portions of said resistance conductor, mountmembers being substantially destroyed during ing said resistance conductor, terminals and supports'within said metallic sheath, so that the supports rest against the ends of said tube, interlocking said supports with said tube to prevent rotary motion or the supports in said sheath, filling said sheath with a powdered heat conducting electri cally insulating material, said opertures in said supports permitting said material to flow from one end to the other 01' said sheath, and then re- I0 er than that of said sheath so that the ends of said tube are removed from the ends of said sheath, winding a resistance conductor into a helical coil, threading the end portions of said coil through a readily destructible support, bringing 7 said end portions adjacent each other to form a providing a tubular member having an external loop, the nexus of which is mounted in said support, providing apertures in said support, inserting said end portions through said sheath so thatsaid support rests against said inner tube, mounting terminals in a similar support, securing said 5 terminals to said end portions of said resistance conductor, mounting said terminals in the end 01' said sheath opposite said first support so that it rests against said inner tube at said other end oi said sheath, filling said sheath with a powdered heat conducting, electrically insulating material, said apertures in said supports permitting said material to flow from one end to the other of said sheath, and then reducing and elongating said sheath and tubeto highly compact said insulating is material.

4. The method of making an electric heater which comprises inserting within a metallic tubular sheath a metallic tube having a length shorter than that of said sheath so that the ends or said 20 tube are removed from the ends of said sheath, threading the end portions or a resistance conductor through a readily destructible support, bringing said end portions adjacent each other to form a loop, the nexus of which is mounted in said support, inserting said end portions through said sheath so that said support rests against oneend oi. said inner tube, mounting terminals in a similarsupport, securing said terminals to said end portions of said resistance conductor, mounting said terminals in the end of said sheath opposite said first support so that it rests against the other end of said inner tube, providing interlocks between said supports and inner tube to prevent rotary and longitudinal movement of said supports in said sheath, filling said sheath with a powdered heat conducting electrically insulating material from one end to the other of said sheath and compacting said insulating material.

5. The method or making a sheathed electric heater having a resistance conductor formed into a loop with its terminal ends adjacent each other at one end of the sheath and supported solely by a mass of insulating material, which comprises diameter substantially qual to the internal diameter of said sheath, forming in one end or said tube a plurality of spaced notches, forming in its I oppomte end a plurality of spaced notches and insaidoppositeendasecondsetoi'spaoednotches spaced from and deeper than the first set, assembling said tube within said sheath so that its ends are removed from the ends otsaid sheath, winding a resistance conductor into a helical coil, threadingtheend portionsor saidcoil through areadily destructible support, bringing said end portions adjacent each other inform a loop, the nexus of which is mounted in said support, providing apertures in said support, giving said support a diameter substantially equal to the internal diameter of said sheath and providing a plurality of spaced projections on its periphery adapted to be received by the notches in said one end or said tube, mountingapairofheadedterminalsinapair 0! supports, one iormed of metal adjacent the heads 01 said terminals and the other of a readily destructlble material removed from said heads and each provided with projectionsarranged to be received in said first'and second set or notches respectively in said'other end oi said tube, securingtheends orsaidruistanceconductortothe ends or said terminals adjacent said destructible support.lnountingsaidterminalsinsaidtube sothatsaidmpporisarereoeivedintheirrespectivenotcheaclosingsaidoneendotsaidsheath which comprises inserting within a metallic tub'ular sheath a metallic tube having a length shorter than that of said sheath so that the ends of said tube are removed from the ends of said sheath, winding a resistance conductor into a helical coil, threading the end portions of said coil through a readily destructible support, bringing said end portions adjacent each other toform a loop, the nexus of which is mounted in said support, providing apertures in said support, inserting said end portions of said conductor through said sheath so that said support rests against said inner tube, mounting terminals in a similar support, securing said terminals to said end portions of said conductor, mounting said terminals in the end of said sheath opposite said first support so that saidsecond support rests against said inner tube atsaid end of said sheath to prevent movement of said support relative to said sheath, providing in the walls of said tube a plurality of elongated longitudinally arranged slots opposite said end portions of said resistance conductor that form the legs of said loop, filling said sheath with a powdered heat conducting, electrically insulating aoaasaa material, said apertures in said supports permitting said material to flow from one end to the other of said sheath, and then reducing and elongating said sheath to highly compact said insulating material.

'7. The method of making an electric heater which comprises inserting within a metallic tubular sheath a metallic tube having a length shorten than that of said sheath so that the ends of said tube are removed from the'ends of said. sheath, threading the end portions of a resistance conductor through a readily destructible support, bringing said end portions adjacent each other to form a loop, the nexus of which is mounted in said I support, providing apertures-in said support, inserting said end portions of said conductor through saidsheath so that said support rests against one end of said inner tube, mounting terminals in a similar support, securing said terminals to said end portions of said conductor, mounting said terminals in the end of said sheath opposite said first'support so that said second sup- 

